Accounting for prepayments in invoices

When I create an invoice, I want there to be a line that indicates if the customer has made a prepayment and subtract that from the total.

The only way I can get something like that is to create an invoice, but not send it, then create a statement for the customer.

Seems like a crappy workaround. Anyone else find a way to do it?

OK, I think I got it figured out.

When you create the order, it is not in invoice yet.

After you create the order you have to convert it to an invoice.

Then the invoice shows the correct balance with the prepayment applied.

This also fixes the problem in my other post about reports.